State-of-the-art lithium ion batteries (LIBs) typically rely on lithium, cobalt, nickel and manganese as part of cathode active material. These metals can be liberated into the environment by inadequate disposal or lack of environmental regulations. Hyperaccumulating plants, which are used for remediation of contaminated soils, can contain high concentrations of these metals.[1,2]

Microwave-assisted digestion and subsequent analysis by inductively coupled plasma-optical emission spectroscopy (ICP-OES) with liquid introduction provides a robust analytical technique for multi-element quantification. However, the elaborate sample preparation using acid digestion is a bottleneck for large sample numbers. In contrast, electrothermal vaporization (ETV)-ICP-OES allows for direct elemental quantification in solid samples. The sample is heated in a graphite furnace while introducing a halogenated reaction gas and transported into the plasma as a dry aerosol.[3]

A quantitative method for the analysis of lithium, nickel, cobalt and manganese in plant samples via ETV-ICP-OES for increased sample throughput should be developed. Achieving robust and accurate quantification of all analytes simultaneously is challenging due to the complex matrix of plant samples. The introduction of a pyrolysis step effectively removed organic matrix to prevent impairments of the plasma conditions during target element liberation. In addition, co-liberation of analytes and high contents of easily ionizable elements (EIEs) complicate the quantification by affecting the plasma. Wet plasma conditions and the introduction of internal standards through a hyphenated cyclone spray chamber were investigated to correct for occurring plasma fluctuations. In addition, overloading the plasma by the introduction of highly concentrated caesium solution was investigated to suppress the effect of varying elemental content in the plasma.

References

[1] J. Henschel et al. Recycling, 2020, 5, 26

[2] R. Schmuch et al. Nature Sustainability, 2018, 1, 495

[3] L. Huang et al. Sample Introduction Systems in ICPMS and ICPOES, 2020, 9, 411.